Segment Reporting - Reconciliation of Income Before Provision for Income Taxes to Distributed Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting [Abstract]
Income before provision for income taxes	$ 285.9	$ 186.1	$ 738.3	$ 1,691.9
Adjustments:
Partner compensation		5.6		(265.4)
Equity-based compensation issued in conjuction with the initial public offering and strategic investments	123.1	93.6	175.2	93.6
Acquisition related charges and amortization of intangibles	52.5	21.5	115.0	45.6
Losses associated with debt refinancing activities			1.9
Other non-operating (income) expenses	(3.3)	0.7	(5.7)	(3.4)
Net income attributable to non-controlling interests in Consolidated entities	(300.0)	(357.9)	(468.0)	(1,222.8)
Provision for income taxes attributable to non-controlling interests in Consolidated entities	(5.7)	(5.7)	(11.7)	(5.7)
Severance and lease terminations	3.5	1.7	4.0	4.1
Other adjustments	(0.2)	(2.8)	0.7	(3.0)
Economic Net Income (loss)	155.8	(57.2)	549.7	334.9
Net Performance Fees	122.5	(106.7)	477.2	228.1
Investment income	6.9	14.0	9.9	37.3
Fee Related Earnings	26.4	35.5	62.6	69.5
Realized performance fees, net of related compensation	117.8	75.8	259.3	218.5
Realized investment income	14.6	4.0	5.3	6.1
Equity-based compensation	$ 4.2	$ 0.6	$ 6.8	$ 0.6
Distributable Earnings	$ 163.0	$ 115.9	$ 334.0	$ 294.7